This invention relates to improvements in a devide for stopping a passenger conveyor such as an escalator or the like.
The stopping of passenger conveyors includes two types, one of which is an emergency stop and the other of which is a normal stop. The emergency stoppage of passenger conveyors is an urgent stop in response to the actuation of a particular safety device or to the depression of an emergency stop pushbutton signaling the occurrence of an emergency. On the other hand, the normal stoppage of passenger conveyors is a stop in the normal manner which is not urgently required for passengers thereon. For example, a passenger conveyor can be stopped by depressing a stop pushbotton for the purpose of changing its traveling speed or reversing its direction of travel. In this cases it is stopped with full knowledge that the passengers ride on the conveyor to increase its load. Alternatively the passenger conveyor can be stopped in response to the energization of an overcurrent relay.
Upon stopping any passenger conveyor, it has been previously a comman practice to disconnect the particular electric motor driving the conveyor from the associated electric source while at the same time deenergizing a mating electromagnet of an electromagnetic brake to brake the electric motor regardless of whether an emergency stop or a normal stop is effected. The braking force exerted by that electromagnetic brake has been usually set to stop the passenger conveyor with such a deceleration that, during an emergency stop it is stopped as quickly as possible, that is to say, passengers riding, for example, on an escalator do not fall down during the "DOWN" travel under the full load which required the longest braking distance. Under other circumstances such as if the electromagnetic brake is applied to the escalator during the "DOWN" travel under a light load or during the "UP" travel in which a load due to the passengers is applied to the escalator, as an additional braking force, then there is a fear that the passengers may fall down due to the deceleration.
Accordingly, it is an object of the present invention to eliminate the disadvantage of the prior art practice as described above by the provision of a passenger conveyor-stopping device capable of safely and reliably stopping the passenger conveyor without an injury such as a violent fall inflicted on any of passengers riding thereon only upon the normal stoppage thereof.